Purity analysis of hydrogen cyanide, cyanogen chloride and phosgene by quantitative ¹³C NMR spectroscopy

Abstract

Hydrogen cyanide, cyanogen chloride and phosgene are produced in tremendously large quantities today by the chemical industry. The compounds are also particularly attractive to foreign states and terrorists seeking an inexpensive mass-destruction capability. Along with contemporary warfare agents, therefore, the US Army evaluates protective equipment used by warfighters and domestic emergency responders against the compounds, and requires their certification at > or = 95 carbon atom % before use. We have investigated the (13)C spin-lattice relaxation behavior of the compounds to develop a quantitative NMR method for characterizing chemical lots supplied to the Army. Behavior was assessed at 75 and 126 MHz for temperatures between 5 and 15 degrees C to hold the compounds in their liquid states, dramatically improving detection sensitivity. T(1) values for cyanogen chloride and phosgene were somewhat comparable, ranging between 20 and 31 s. Hydrogen cyanide values were significantly shorter at 10-18 s, most likely because of a (1)H--(13)C dipolar contribution to relaxation not possible for the other compounds. The T(1) measurements were used to derive relaxation delays for collecting the quantitative (13)C data sets. At 126 MHz, only a single data acquisition with a cryogenic probehead gave a signal-to-noise ratio exceeding that necessary for certifying the compounds at > or = 95 carbon atom % and 99% confidence. Data acquired at 75 MHz with a conventional probehead, however, required > or = 5 acquisitions to reach this certifying signal-to-noise ratio for phosgene, and >/= 12 acquisitions were required for the other compounds under these same conditions. In terms of accuracy and execution time, the NMR method rivals typical chromatographic methods.

Nitryl Cyanide, NCNO2

“…The 13 C NMR spectrum shows one signal at 106.6 ppm, which is similar to those observed for a range of compounds, such as ClCN (95.5) and HCN (111.5 ppm),11 and features the expected 1:1:1 triplet pattern, which is due to coupling with 14 N ( I =1) with J ( 13 C– 14 N)=25 Hz (Figure 3). In the 14 N NMR spectrum (Figure 3), however, this coupling could not be observed, as the quadrupole moment of 14 N leads to signal broadening.…”

A Dimer of Hydrogen Cyanide Stabilized by a Lewis Acid

“…At 0 8 8C, decomposition of 1 was observed within 2hand at À20 8 8Cwithin 8h,affording ahighly viscous black material. [55,56] Hence,f reshly prepared crystals or solutions were always needed for any further studies.…”

Characterization of Chemical Weapons Convention Schedule 3 Compounds by Quantitative 13C NMR Spectroscopy

“…Quantitative NMR analyses are typically reported for 'H, 4 -6 13 C 7-9 and 3 1p0-12 spectroscopy, however, quantitative spectroscopy for other nuclei 1 [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] can also be found. Further, the accuracy and precision of NMR signal intensity measurements have recently been reviewed, 20 and more recently, Maniara et al 2 reported a systematic validation of the quantitative NMR method.…”